[Spoilers] Rethinking the Twelve

[RenewalXVII]

I personally thought he was talking about the title of the 14th Convocation member at the time, like how Elidbus is Emissary, Lahabrea is Speaker and Emet himself is Architect.... but looking back on it it seems more likely he was talking about the Lightwardens' Light. Like he is wondering that the stress of battle caused us to actually succumb, but then realizes it's the power of the Blessing.

Just adding to this for further confirmation, the text box for the fight specifically says Wardens, plural. It's 100% referring to the Lightwardens, unless one wants to suppose it's a typo.